My son is a vegan and his top choice is Beyond Meat bratwurst for sausages, and Impossible Burgers for a burger substitute. I've tried many of them and in my opinion the options that don't try as hard to impersonate meat are better. I like black bean 'burgers' (my son makes these from scratch), and there is one artichoke based patty that is pretty good, but I don't recall the brand.
For reduction in environmental impact the best first step is to reduce beef and lamb consumption. Replacing two beef meals with chicken likely has more environmental impact than replacing one beef meal with a vegan product. I always also note that the packaging on vegan meat substitutes is outrageous. A ton of packaging for two small patties for a product trying to be environmentally conscious. I also question the health benefits of these products given how highly processed they are, but for most Americans, they are probably better than meat.
Enjoy!